An economic source of industrial hydrogen is required to produce liquid and gaseous fuels from coal, for hydrodesulfurization of heavy or light oils, for the hydrogenation of mineral or fatty oils, and for the operation of fuel cells. Whereas industrial hydrogen has been produced largely from natural gas and naphtha, recent shortages and price movements have dictated a change to the use of coal as a raw material.
Accordingly, hydrogen is produced by the gasification of coal with oxygen and steam. This technique is used to produce a synthesis gas which is cleaned to remove acid gases and then reacted in stages with steam over catalysts to convert the carbon monoxide to hydrogen, and carbon dioxide is separated as a by-product of this reaction. The process of obtaining hydrogen from coal involves a complex sequence of operations and entails losses of considerable energy from the fuel in the process. The technical difficulties are even greater if the process is carried out under pressures of from 50 to 200 atmospheres, which leads to problems in injecting fuel solids and in handling oxygen.
Hydrogen is also produced by the electrolysis of water from an aqueous solution of potassium hydroxide. Although the minimum energy of decomposition corresponds with a cell potential of 1.229 volt, the voltage of commercial hydrogen cells is more than twice this minimum potential because of electrode polarization and the electrical resistance of the electrolyte and the diaphragm which is necessary to separate the hydrogen from the oxygen which is generated at the anode.
It is an object of this invention to provide an improved process for preparing hydrogen from carbonaceous fuels. This and other objects are set forth in greater detail in the following description of the invention.